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The Beaufort Wind Scale

The Beaufort scale was long in use as a system for estimating wind speeds.

It was introduced in 1805 by Admiral Sir Francis Beaufort (1774-1857) of the British navy to describe wind effects on a fully rigged man-of-war sailing vessel, and it was later extended to include descriptions of effects on land features as well.
 

Bft.
Sourroundings
Wind     
Knots
km/h
mph
m/s
0
Smoke rises vertically and the see is mirror smooth  calm
0
0
0
0
1
Smokes moves slightly with breeze and  shows direction of wind light air
1-3
1-5
1-3
<2
2
You can feel wind on your face and hear the leaves start to rustle light breeze
4-6
6-11
4-7
2-3
3
Smoke will move horizontally and small branches start to sway. Wind extends a light flag gentle breeze
7-10
12-19
8-12
4-5
4
Loose dust or sand on the ground will move and larger branches will sway, loose paper blows around, and fairly frequent whitecaps occur moderate breeze
11-16
20-28
13-18
6-7
5
Surface waves form on water and small trees sway  fresh breeze
17-21
29-38
19-24
8-10
6
Trees begin to bend with the force of the wind and causes whistling in telephone wires and some spray on the sea surface strong breeze
22-27
39-49
25-31
11-13
7
large trees sway moderate gale
28-33
50-61
32-38
14-16
8
twigs break from trees, and long streaks of foam appear on the ocean fresh gale
34-40
62-74
39-46
17-20
9
branches break from trees strong gale
41-47
75-88
47-55
21-24
10
weak trees are uprooted, and the sea takes on a white appearance whole gale
48-55
89-102
56-64
25-28
11
widespread damage storm
56-63
103-117
65-73
29-32
12
structural damage on land and storm waves at sea hurricane
>64
>118
>74
>33